Melanic morphs of Bactrocera dorsalis possess distinct developmental time, weight, and wing size and shape

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AbstractThe scutum of oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), shows a high degree of variability in its colouration, which goes from black to red‐brown. Such variation depicts different levels of melanin production in these individuals. In insects, melanization can have an effect on their fitness parameters, which could consequently impact the insect's adaptive responses. Here, we asked whether the progeny produced by B. dorsalis individuals with different scutum colouration (melanic morphs) would differ in their developmental time, weight, and wing size and shape. To address this, we followed eggs produced by each B. dorsalis melanic morph by recording their pupation time, emergence time, and larval (second instar), pupal, and adult weights. Also, using landmark‐based geometric morphometric analysis, we assessed the variation in wing size and shape of the adults obtained from each parental melanic morphs of B. dorsalis. We found that larvae produced by adults with the darkest scutum exhibited faster development and weighed more than those produced by adults with brown scutum. At the adult stage, individuals from parents with darker and brown scutum had a reduced weight and wing size (length, width, area, and centroid size) than those from parents with moderate melanin production. We also found significant wing shape variation across the four melanic morphs. Our study suggests that melanisation in the scutum of B. dorsalis has a fitness gain in the preimaginal stages of this fly. In the adult stage, however, the amount of melanin in the scutum has a fitness cost. This suggests that in B. dorsalis, there is a potential trade‐off between melanin production and fitness parameters, which could have implications for adaptive responses such as thermoregulation, flight, and dispersal, and consequently for its management.